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To: dsterba@suse.cz, Christophe Leroy , erhard_f@mailbox.org, Chris Mason , Josef Bacik , David Sterba , Andrew Morton , linux-mm@kvack.org, stable@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-kernel@vger.kernel.org, linux-btrfs@vger.kernel.org References: <20190826153757.GW2752@twin.jikos.cz> From: Nikolay Borisov Openpgp: preference=signencrypt Autocrypt: addr=nborisov@suse.com; prefer-encrypt=mutual; keydata= mQINBFiKBz4BEADNHZmqwhuN6EAzXj9SpPpH/nSSP8YgfwoOqwrP+JR4pIqRK0AWWeWCSwmZ T7g+RbfPFlmQp+EwFWOtABXlKC54zgSf+uulGwx5JAUFVUIRBmnHOYi/lUiE0yhpnb1KCA7f u/W+DkwGerXqhhe9TvQoGwgCKNfzFPZoM+gZrm+kWv03QLUCr210n4cwaCPJ0Nr9Z3c582xc bCUVbsjt7BN0CFa2BByulrx5xD9sDAYIqfLCcZetAqsTRGxM7LD0kh5WlKzOeAXj5r8DOrU2 GdZS33uKZI/kZJZVytSmZpswDsKhnGzRN1BANGP8sC+WD4eRXajOmNh2HL4P+meO1TlM3GLl EQd2shHFY0qjEo7wxKZI1RyZZ5AgJnSmehrPCyuIyVY210CbMaIKHUIsTqRgY5GaNME24w7h TyyVCy2qAM8fLJ4Vw5bycM/u5xfWm7gyTb9V1TkZ3o1MTrEsrcqFiRrBY94Rs0oQkZvunqia c+NprYSaOG1Cta14o94eMH271Kka/reEwSZkC7T+o9hZ4zi2CcLcY0DXj0qdId7vUKSJjEep c++s8ncFekh1MPhkOgNj8pk17OAESanmDwksmzh1j12lgA5lTFPrJeRNu6/isC2zyZhTwMWs k3LkcTa8ZXxh0RfWAqgx/ogKPk4ZxOXQEZetkEyTFghbRH2BIwARAQABtCNOaWtvbGF5IEJv cmlzb3YgPG5ib3Jpc292QHN1c2UuY29tPokCOAQTAQIAIgUCWIo48QIbAwYLCQgHAwIGFQgC CQoLBBYCAwECHgECF4AACgkQcb6CRuU/KFc0eg/9GLD3wTQz9iZHMFbjiqTCitD7B6dTLV1C ddZVlC8Hm/TophPts1bWZORAmYIihHHI1EIF19+bfIr46pvfTu0yFrJDLOADMDH+Ufzsfy2v HSqqWV/nOSWGXzh8bgg/ncLwrIdEwBQBN9SDS6aqsglagvwFD91UCg/TshLlRxD5BOnuzfzI Leyx2c6YmH7Oa1R4MX9Jo79SaKwdHt2yRN3SochVtxCyafDlZsE/efp21pMiaK1HoCOZTBp5 VzrIP85GATh18pN7YR9CuPxxN0V6IzT7IlhS4Jgj0NXh6vi1DlmKspr+FOevu4RVXqqcNTSS E2rycB2v6cttH21UUdu/0FtMBKh+rv8+yD49FxMYnTi1jwVzr208vDdRU2v7Ij/TxYt/v4O8 V+jNRKy5Fevca/1xroQBICXsNoFLr10X5IjmhAhqIH8Atpz/89ItS3+HWuE4BHB6RRLM0gy8 T7rN6ja+KegOGikp/VTwBlszhvfLhyoyjXI44Tf3oLSFM+8+qG3B7MNBHOt60CQlMkq0fGXd mm4xENl/SSeHsiomdveeq7cNGpHi6i6ntZK33XJLwvyf00PD7tip/GUj0Dic/ZUsoPSTF/mG EpuQiUZs8X2xjK/AS/l3wa4Kz2tlcOKSKpIpna7V1+CMNkNzaCOlbv7QwprAerKYywPCoOSC 7P25Ag0EWIoHPgEQAMiUqvRBZNvPvki34O/dcTodvLSyOmK/MMBDrzN8Cnk302XfnGlW/YAQ csMWISKKSpStc6tmD+2Y0z9WjyRqFr3EGfH1RXSv9Z1vmfPzU42jsdZn667UxrRcVQXUgoKg QYx055Q2FdUeaZSaivoIBD9WtJq/66UPXRRr4H/+Y5FaUZx+gWNGmBT6a0S/GQnHb9g3nonD jmDKGw+YO4P6aEMxyy3k9PstaoiyBXnzQASzdOi39BgWQuZfIQjN0aW+Dm8kOAfT5i/yk59h VV6v3NLHBjHVw9kHli3jwvsizIX9X2W8tb1SefaVxqvqO1132AO8V9CbE1DcVT8fzICvGi42 FoV/k0QOGwq+LmLf0t04Q0csEl+h69ZcqeBSQcIMm/Ir+NorfCr6HjrB6lW7giBkQl6hhomn l1mtDP6MTdbyYzEiBFcwQD4terc7S/8ELRRybWQHQp7sxQM/Lnuhs77MgY/e6c5AVWnMKd/z MKm4ru7A8+8gdHeydrRQSWDaVbfy3Hup0Ia76J9FaolnjB8YLUOJPdhI2vbvNCQ2ipxw3Y3c KhVIpGYqwdvFIiz0Fej7wnJICIrpJs/+XLQHyqcmERn3s/iWwBpeogrx2Lf8AGezqnv9woq7 OSoWlwXDJiUdaqPEB/HmGfqoRRN20jx+OOvuaBMPAPb+aKJyle8zABEBAAGJAh8EGAECAAkF AliKBz4CGwwACgkQcb6CRuU/KFdacg/+M3V3Ti9JYZEiIyVhqs+yHb6NMI1R0kkAmzsGQ1jU zSQUz9AVMR6T7v2fIETTT/f5Oout0+Hi9cY8uLpk8CWno9V9eR/B7Ifs2pAA8lh2nW43FFwp IDiSuDbH6oTLmiGCB206IvSuaQCp1fed8U6yuqGFcnf0ZpJm/sILG2ECdFK9RYnMIaeqlNQm iZicBY2lmlYFBEaMXHoy+K7nbOuizPWdUKoKHq+tmZ3iA+qL5s6Qlm4trH28/fPpFuOmgP8P K+7LpYLNSl1oQUr+WlqilPAuLcCo5Vdl7M7VFLMq4xxY/dY99aZx0ZJQYFx0w/6UkbDdFLzN upT7NIN68lZRucImffiWyN7CjH23X3Tni8bS9ubo7OON68NbPz1YIaYaHmnVQCjDyDXkQoKC R82Vf9mf5slj0Vlpf+/Wpsv/TH8X32ajva37oEQTkWNMsDxyw3aPSps6MaMafcN7k60y2Wk/ TCiLsRHFfMHFY6/lq/c0ZdOsGjgpIK0G0z6et9YU6MaPuKwNY4kBdjPNBwHreucrQVUdqRRm RcxmGC6ohvpqVGfhT48ZPZKZEWM+tZky0mO7bhZYxMXyVjBn4EoNTsXy1et9Y1dU3HVJ8fod 5UqrNrzIQFbdeM0/JqSLrtlTcXKJ7cYFa9ZM2AP7UIN9n1UWxq+OPY9YMOewVfYtL8M= Message-ID: Date: Mon, 26 Aug 2019 18:40:24 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190826153757.GW2752@twin.jikos.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 26.08.19 =D0=B3. 18:37 =D1=87., David Sterba wrote: > On Wed, Aug 21, 2019 at 03:05:55PM +0000, Christophe Leroy wrote: >> Various notifications of type "BUG kmalloc-4096 () : Redzone >> overwritten" have been observed recently in various parts of >> the kernel. After some time, it has been made a relation with >> the use of BTRFS filesystem. >> >> [ 22.809700] BUG kmalloc-4096 (Tainted: G W ): Redzone= overwritten >> [ 22.809971] -------------------------------------------------------= ---------------------- >> >> [ 22.810286] INFO: 0xbe1a5921-0xfbfc06cd. First byte 0x0 instead of = 0xcc >> [ 22.810866] INFO: Allocated in __load_free_space_cache+0x588/0x780 = [btrfs] age=3D22 cpu=3D0 pid=3D224 >> [ 22.811193] __slab_alloc.constprop.26+0x44/0x70 >> [ 22.811345] kmem_cache_alloc_trace+0xf0/0x2ec >> [ 22.811588] __load_free_space_cache+0x588/0x780 [btrfs] >> [ 22.811848] load_free_space_cache+0xf4/0x1b0 [btrfs] >> [ 22.812090] cache_block_group+0x1d0/0x3d0 [btrfs] >> [ 22.812321] find_free_extent+0x680/0x12a4 [btrfs] >> [ 22.812549] btrfs_reserve_extent+0xec/0x220 [btrfs] >> [ 22.812785] btrfs_alloc_tree_block+0x178/0x5f4 [btrfs] >> [ 22.813032] __btrfs_cow_block+0x150/0x5d4 [btrfs] >> [ 22.813262] btrfs_cow_block+0x194/0x298 [btrfs] >> [ 22.813484] commit_cowonly_roots+0x44/0x294 [btrfs] >> [ 22.813718] btrfs_commit_transaction+0x63c/0xc0c [btrfs] >> [ 22.813973] close_ctree+0xf8/0x2a4 [btrfs] >> [ 22.814107] generic_shutdown_super+0x80/0x110 >> [ 22.814250] kill_anon_super+0x18/0x30 >> [ 22.814437] btrfs_kill_super+0x18/0x90 [btrfs] >> [ 22.814590] INFO: Freed in proc_cgroup_show+0xc0/0x248 age=3D41 cpu= =3D0 pid=3D83 >> [ 22.814841] proc_cgroup_show+0xc0/0x248 >> [ 22.814967] proc_single_show+0x54/0x98 >> [ 22.815086] seq_read+0x278/0x45c >> [ 22.815190] __vfs_read+0x28/0x17c >> [ 22.815289] vfs_read+0xa8/0x14c >> [ 22.815381] ksys_read+0x50/0x94 >> [ 22.815475] ret_from_syscall+0x0/0x38 >> >> Commit 69d2480456d1 ("btrfs: use copy_page for copying pages instead >> of memcpy") changed the way bitmap blocks are copied. But allthough >> bitmaps have the size of a page, they were allocated with kzalloc(). >> >> Most of the time, kzalloc() allocates aligned blocks of memory, so >> copy_page() can be used. But when some debug options like SLAB_DEBUG >> are activated, kzalloc() may return unaligned pointer. >> >> On powerpc, memcpy(), copy_page() and other copying functions use >> 'dcbz' instruction which provides an entire zeroed cacheline to avoid >> memory read when the intention is to overwrite a full line. Functions >> like memcpy() are writen to care about partial cachelines at the start >> and end of the destination, but copy_page() assumes it gets pages. As >> pages are naturally cache aligned, copy_page() doesn't care about >> partial lines. This means that when copy_page() is called with a >> misaligned pointer, a few leading bytes are zeroed. >> >> To fix it, allocate bitmaps through kmem_cache instead of using kzallo= c() >> The cache pool is created with PAGE_SIZE alignment constraint. >> >> Reported-by: Erhard F. >> Link: https://bugzilla.kernel.org/show_bug.cgi?id=3D204371 >> Fixes: 69d2480456d1 ("btrfs: use copy_page for copying pages instead o= f memcpy") >> Cc: stable@vger.kernel.org >> Signed-off-by: Christophe Leroy >> --- >> v2: Using kmem_cache instead of get_zeroed_page() in order to benefit = from SLAB debugging features like redzone. >=20 > I'll take this version, thanks. Though I'm not happy about the allocato= r > behaviour. The kmem cache based fix can be backported independently to > 4.19 regardless of the SL*B fixes. >=20 >> +extern struct kmem_cache *btrfs_bitmap_cachep; >=20 > I've renamed the cache to btrfs_free_space_bitmap_cachep >=20 > Reviewed-by: David Sterba Isn't this obsoleted by '[PATCH v2 0/2] guarantee natural alignment for kmalloc()' ? >=20